CVE-2021-27851

A security vulnerability that can lead to local privilege escalation has
been found in ’guix-daemon’. It affects multi-user setups in which
’guix-daemon’ runs locally. The attack consists in having an unprivileged
user spawn a build process, for instance with guix build, that makes its
build directory world-writable. The user then creates a hardlink to a
root-owned file such as /etc/shadow in that build directory. If the user
passed the --keep-failed option and the build eventually fails, the daemon
changes ownership of the whole build tree, including the hardlink, to the
user. At that point, the user has write access to the target file. Versions
after and including v0.11.0-3298-g2608e40988, and versions prior to
v1.2.0-75109-g94f0312546 are vulnerable.

Bugs

• <http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=985467&gt;